It is known that, in a gas engine utilized in power generating equipment, high power generation efficiency is obtained by controlling the ignition timing to be advanced before the top dead center by a predetermined angle. However, in a case where the ignition timing is advanced, there is a problem of knocking.
For example, Patent Literature 1 discloses a gas engine system intended for power generating equipment, in which the ignition timing is adjusted such that a delay calculation value of a knocking occurrence ratio (e.g., a moving average value) becomes a target occurrence ratio. In this gas engine system, it is determined, for each cycle, based on the pressure in the cylinder whether or not allowable knocking has occurred. The knocking occurrence ratio means the ratio of the number of cycles in which allowable knocking has occurred to a predetermined number of cycles. In the gas engine system, if the delay calculation value of the knocking occurrence ratio is lower than the target occurrence ratio, the ignition timing is advanced based on the difference between the delay calculation value of the knocking occurrence ratio and the target occurrence ratio. If the delay calculation value of the knocking occurrence ratio is higher than the target occurrence ratio, the ignition timing is retarded based on the difference between the delay calculation value of the knocking occurrence ratio and the target occurrence ratio.
In the gas engine system disclosed by Patent Literature 1, in a case where the ignition timing is advanced, the advance speed is limited to a preset advance rate or lower.